It is well known to produce laminated structures by joining sheets of similar or dissimilar materials together. The layers may be joined by any one of a large number of methods. In order to maximise the strength of the structure the layers are bonded together over substantially over all of the surface areas which are in contact. This can be achieved using an adhesive, a thermal bond or compression moulding technique. However, in some cases there is no satisfactory bonding method available to join the materials. This may be because the chemical compositions of the materials are such that they are incompatible with the same adhesives. For example, an adhesive may provide a good bond to one material, but bond weakly or not at all to a different material.
This problem is normally overcome by choosing materials which can be bonded successfully to one another. However, such combinations may result in the finished component having non optimal structural or functional characteristics. For example, it is known to manufacture aerodynamic vanes for turbo machinery from composite materials such as glass fibre or carbon fibre. Such vanes are advantageously lightweight and rigid.
However, they are also brittle, can be easily weakened by impact from foreign objects and vulnerable to erosion. It is common to provide a shield on the leading edge of such aerofoils in the form of a metal strip. Unfortunately, in the eventuality of the strip being released from the vane, there is a high risk of it causing damage to components downstream of the vane.
It would therefore be advantageous to shield the composite material using a material which has high impact resistance but which is less likely to cause damage if it becomes detached, such as, for example, a thermoplastic. However, glass and carbon fibre materials are not easily bonded to thermoplastics, so despite such a material combination in a laminated structure being advantageous for impact and erosion protection, it is not achievable without risking detachment of the protective layer, thereby removing the advantage of such a material selection.
Hence a laminate structure in which a bond can be made between dissimilar materials is highly desirable.